Upgrade to Undertow 2.0.20.Final

Closes gh-16767

Author: snicoll

spring-boot-project/spring-boot-dependencies/pom.xml

@@ -189,7 +189,7 @@
 		<thymeleaf-extras-java8time.version>3.0.4.RELEASE</thymeleaf-extras-java8time.version>
 		<tomcat.version>9.0.19</tomcat.version>
 		<unboundid-ldapsdk.version>4.0.10</unboundid-ldapsdk.version>
-		<undertow.version>2.0.19.Final</undertow.version>
+		<undertow.version>2.0.20.Final</undertow.version>
 		<webjars-hal-browser.version>3325375</webjars-hal-browser.version>
 		<webjars-locator-core.version>0.35</webjars-locator-core.version>
 		<wsdl4j.version>1.6.3</wsdl4j.version>